Prior hereto, the applicant of the present invention developed the engine vibrator absorbing flywheel described in Japanese patent application No. 60-44298 and corresponding U.S. patent application Ser. No. 836,365, now U.S. Pat. No. 4,751,993, dated June 21, 1988, and West Germany patent application No. P 36 07 3989-13 which are based on the Japanese patent application No. 60-44298.
In such prior flywheel, as shown in FIG. 5 hereof, a first flywheel 104 is fastened to an engine crank shaft 100 and engaged and disengaged by a clutch disc 102; a second flywheel 106 is installed concentrically with the first flywheel and set to a specified mass; a damper mechanism 108 resiliently couples the flywheels to each other; and, a friction damping mechanism 105 transmits output from the second flywheel 106 to spline hub 103 of the clutch disc 102 and damps vibration only when the clutch disc 102 contacts the first flywheel 104.
As shown in FIG. 6 hereof, the first flywheel 104 and second flywheel 106 absorb vibration transmitted from the crank shaft 100 with power, and the frictional damping mechanism 105 damps the vibration.
However, in such prior flywheel assembly hysteresis torque Thd generates between the hub flange 103 of the clutch disc 102 and the side plate 109 (FIG. 5). In some cases, the hysteresis torque Thd have an undesirable influence upon damping characteristics.
Further, the damping function of the frictional damping mechanism 106 for the second flywheel 106 comes to a stop, during clutch releasing operation in which the clutch disc 102 is disconnected from the first flywheel 104. It is possible that the second flywheel will have a resonance phenomenon depending on the frequency of the inputted vibration.